Coenzyme Q10 deficiency

Coenzyme Q10 (CoQ10) deficiency, also known as ubiquinone deficiency, is a rare inherited mitochondrial disorder characterized by reduced levels of coenzyme Q10, a critical component of the mitochondrial electron transport chain essential for cellular energy production and antioxidant defense. Because CoQ10 is vital for energy metabolism in virtually all cells, its deficiency can affect multiple organ systems, though the clinical presentation is highly variable. Several distinct clinical phenotypes have been described, including a severe infantile multisystemic form, an encephalomyopathic form with seizures and ataxia, a cerebellar ataxia form (the most common presentation), a nephropathy-predominant form with steroid-resistant nephrotic syndrome, and an isolated myopathic form. Key symptoms may include progressive cerebellar ataxia, muscle weakness, exercise intolerance, seizures, intellectual disability, kidney dysfunction (nephrotic syndrome), sensorineural hearing loss, and optic atrophy. The severity ranges from fatal neonatal presentations to milder adult-onset disease. Primary CoQ10 deficiency is caused by pathogenic variants in genes directly involved in CoQ10 biosynthesis (such as COQ2, COQ4, COQ6, COQ7, COQ8A/ADCK3, COQ8B/ADCK4, COQ9, PDSS1, and PDSS2), while secondary deficiency can arise from defects in other mitochondrial or metabolic pathways. Importantly, CoQ10 deficiency is one of the few mitochondrial disorders with an available treatment: oral CoQ10 (ubiquinone) or ubiquinol supplementation can improve symptoms in many patients, particularly if initiated early. Response to supplementation varies depending on the phenotype and the degree of organ damage at the time of diagnosis, with renal and cerebellar forms often showing the best response when treated promptly.

Common questions about Coenzyme Q10 deficiency